Old, well-used holsters sometimes become loose. If the leather is still in good shape, you don't need a new rigŚyou can re-fit the old one. Here's how:

Wet the old holster in cold water. It should be wet, slightly darkened, but not sopping. If you get it too wet, use paper towelling to sop up as much water as you can, and let it dry a little in a cool, dry place. Do not use any kind of heat.

Oil or grease the pistol.

Put the gun into a thin-wall plastic bag.

Shove the bagged gun into the holster, as far as it will go.

Using smooth shapes, for instance a butter-knife handle and a couple of sizes of spoons, carefully press-mold ("bone") the leather tightly around the shape of the pistol.

With the pistol still inside, put the holster into a cool, dry place, and let it dry all on its own.

When it's almost completely dry, "bone" the leather around the gun some more, just to be sure.

Now very carefully pull the bagged gun out of the holster without disturbing your "boning" job.